The inheritance of shikimate dehydrogenase (SDH) allozymes, and their linkage relationships with phosphoglucoisomerase (PGI-2) and a locus governing red versus yellow fruit color were studied in the diploid (2n = 2x = 14) strawberry. SDH behaved as a monomeric enzyme with alternate, codominant alleles at a single locus. In the F2 generation of reciprocal crosses between Fragaria vesca Alpine cultivars Baron Solemacher (red fruit) and Yellow Wonder (yellow fruit), SDH segregated in a 1:2:1 ratio, and fruit color segregated 3 red/1 yellow. The SDH and fruit color segregations were highly correlated, with a recombination frequency of 1.1%. Diploid USDA accession FRA 364 was heterozygous with respect to both SDH and PGI-2. Both isozymes segregated 1:1, and assorted independently of each other in the F1 generation of crosses between FRA 364 (as male) and the two Alpine cultivars. The close (1.1 cM) linkage detected between the SDH and fruit color loci constitutes the first report of quantified genetic linkage in the strawberry

Ten codominant RAPD markers, ranging in size from about 300 to about 1350 bp, were identified in mapping populations of chickpea (Cicer arietinum L.) and diploid strawberry (Fragaria vesca L.). A distinguishing feature of all ten markers, and perhaps of codominant RAPD markers in general, was the presence in heterozygous individuals of a non-parental, heteroduplex band migrating more slowly than either of the respective parental bands. This non-parental band could also be generated by mixing parental DNAs before PCR (template mixing). As a means of identifying primers likely to detect codominant RAPD markers, parental and mixed-template (parent-parent) PCR-product gel lanes were compared for 20 previously untested RAPD primers (10-base oligomers). Four primers that produced a total of five non-parental, heteroduplex bands in mixed-template reactions were selected, and then used to detect a total of five segregating, codominant markers and nine dominant markers in the respective F2 mapping population, a codominant marker frequency of 35.7%. When closely migrating fast and slow bands of codominant RAPDs were difficult to differentiate, parent-progeny template mixing was used to deliberately generate heteroduplex bands in fast- or slow-band F2 homozygotes, respectively, allowing confirmation of marker phenotype.

For the purpose of developing an in vitro regeneration system for chickpea (Cicer arietinum L.), an important food legume, immature cotyledons approximately 5 mm long were excised from developing embryos and cultured on B5 basal medium supplemented with 1.5% sucrose and various growth regulator combinations. Only non-morphogenic callus was formed in response to concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), naphthaleneacetic acid (NAA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) previously reported to induce somatic embryogenesis on immature soybean cotyledons. However, 4.6, 13.7, and 45.6 μM zeatin induced formation of white, cotyledon-like structures (CLS) at the proximal end of immature cotyledons placed with adaxial surface facing the agar medium. No morphogenesis, or occasional formation of fused, deformed CLS, was observed when zeatin was replaced with kinetin or 6-benzyladenine, respectively. The highest response frequency, 64% of explants forming CLS, was induced by 13.7 μM zeatin plus 0.2 μM indole-acetic acid (IAA). Within 20–40 days culture on zeatin, shoots formed at the base of CLS on approximately 50% of CLS-bearing explants, and proliferated upon subsequent transfer to basal medium with 4.4 μM BA or 4.6 μM kinetin. This regeneration system may be useful for genetic transformation of chickpea.

The allelic and linkage relationships among five chickpea (Cicer arietinum L.) morphological markers were investigated. When crossed with purple-flowered line ICC 640 and with each other, white flowered variety ‘UC5’ and mutant line PM974 were shown to carry non-allelic, single recessive genes for white flower color, provisionally designated w1 and w2, respectively. The single recessive gene conferring simple leaves in mutant PM299 was allelic to the previously described slv gene carried by variety ‘Surutato 77’, line ICC 10301, and other simple leaf chickpea mutants. In mutant 756M, a filiform leaf trait was controlled by a single recessive gene, fil, which was non-allelic to slv.

The fil and w2 genes were linked, with recombination frequencies of 0.05 and 0.14 estimated from results of coupling and repulsion phase crosses, respectively. fil and w1 segregated independently. Root nodulation gene rn3 was closely linked to slv: recombination frequencies of 0.05 and 0.11 were estimated from results of coupling and repulsion phase crosses, respectively. A loose linkage detected between the w2-fil and the rn3-slv linkage groups will be the subject of further scrutiny.

Two genetic variants with increased organ size were independently derived from diploid (2n = 2x = 16) chickpea (Cicer arietinum L.) line ICC 640. Radiation-induced mutant PM 101 had greatly enlarged leaves, leaflets, and pods, and an elongated stem with longer intemodes but fewer nodes than ICC 640. F1, F2, and F3 data from crosses with ICC 640 showed that the mutant characteristics of PM 1 101 were the pleiotropic effects of a single, recessive genetic factor. For purposes of comparison, tetraploid derivatives of ICC 640 were produced by colchicine treatment of seed. In the tetraploids, leaflets and pods were enlarged, but less dramatically than in PM 1 101. Enlarged pollen grains and stomatal guard cells, and increased guard cell chloroplast number were found in tetraploids but not in PM 1 101, while both variants produced fewer seeds than ICC 640. Mutant PM 1 101 and the tetraploids represent two very different manifestations of gigantism in chickpea.

Non-nodulating chickpea (Cicer arietinum L.) mutant PM233B was characterized anatomically via comparison with its normally nodulating parent line ICC 640. Root hair and cortical cell infection threads, cortical cell division centers, and nodule formation were observed by light microscopy in serial root sections of ICC 640, but were absent in PM233B. Scanning electron microscope observations of inoculated root sections showed that ICC 640 and PM233B were indistinguishable in adsorption of chickpea Rhizobium strain CC1192. Thus, the rhizobial infection process was blocked in PM233B at a stage subsequent to root hair adsorption of bacteria, but prior to initiation of infection threads and root cortical cell division. Reciprocal shoot grafts between ICC 640 and PM233B demonstrated that the non-nodulation phenotype of PM233B was controlled by the root, and not the shoot, genotype. Key words: chickpea, Cicer arietinum, root nodule, symbiosis, non-nodulating mutant.

Genetic analysis of the ineffectively nodulating radiation-induced chickpea mutants PM405 and PM796 revealed two new recessive, nonallelic root nodulation genes. In PM405, the m4 gene determined the formation of small white nodules; in PM796, the m5 gene determined the formation of nodules that were green except for a narrow band apparent leghemoglobin pigmentation near the nodule tip. Recessive epistasis was evident in crosses between PM405 and PM796. F₂ segregation data fit the expected ratio of 9 wild type: 3 PM796 type: 4 PM405 type.

In continuing investigations of host genetic control of nodulation in the Rhizobium-chickpea (Cicer arietinum L.) symbiosis, three γ-irradiation-induced mutants resistant to nodulation by Rhizobium strain CC1192 were characterized. When root temperature was controlled under greenhouse conditions, mutants PM665 and PM679 produced effective nodules at 24°C, but nodulation was strongly suppressed (PM665) or eliminated (PM679) at 29°C. Wild-type parent P502 was effectively nodulated at both temperatures, but lacked nodules at 34°C. Mutant PM233 did not form nodules at any temperature tested. In trials with 16 other strains of Rhizobium that formed effective root nodules on P502, no nodules formed on PM233, and only a few nodule-like protuberances formed on PM665 and PM679 when roots were maintained at 29°. In addition to the non-nodulating (Nod⁻) phenotype, PM665 also produced ledlets with aberrant trichomes that were characterized by scanning electron microscopy. Genetic studies showed that recessive alleles at three different loci were responsible for the Nod⁻ phenotypes in PM233, PM665, and PM679. Progeny from all crosses involving PM665 showed cosegregation of the Nod⁻ phenotype and the aberrant trichome trait. On the basis of data presented, it is proposed that the symbols rn1, rn2, and rn3 be assigned to the loci producing the Nod⁻ phenotype in mutants PM233, PM665, and PM679, respectively.

As a first step toward future studies of symbiotic N₂ fixation in chickpea (Cicer arietinum L.), genotypes exhibiting aberrant responses to inoculation with Rhizobium strain CC1192 were isolated by selection following γ,-irradiation mutagenesis of chickpea line P502. In greenhouse experiments, 28 of 968 M₂ families contained one or more plants which showed stunted, chlorotic growth after 30 to 35 days under N₂-dependent conditions but which resumed vigorous growth with the addition of 8 mM NH₄NO₅. Of 24 selections advanced to the M₄generation, two lines, PM233 and PM665, rep:roducibly failed to form root nodules under various conditions where the parental control P502 was well nodulated. PM233 and PM665 grew vigorously with 8 mM NH₄NO₅, but PM665 could be distinguished from the wild type by lighter green leaves and slightly crinkled pods. Six other lines exhibited aberrant responses to inoculation in replicated M₄-generation testing, but have not yet been satisfactorily characterized.